+/// isOnlyReachableViaFallthough - Return true if this basic block has
+/// exactly one predecessor and the control transfer mechanism between
+/// the predecessor and this block is a fall-through.
+bool MachineBasicBlock::isOnlyReachableByFallthrough() const {
+ // If this is a landing pad, it isn't a fall through. If it has no preds,
+ // then nothing falls through to it.
+ if (isLandingPad() || pred_empty())
+ return false;
+
+ // If there isn't exactly one predecessor, it can't be a fall through.
+ const_pred_iterator PI = pred_begin(), PI2 = PI;
+ ++PI2;
+ if (PI2 != pred_end())
+ return false;
+
+ // The predecessor has to be immediately before this block.
+ const MachineBasicBlock *Pred = *PI;
+
+ if (!Pred->isLayoutSuccessor(this))
+ return false;
+
+ // If the block is completely empty, then it definitely does fall through.
+ if (Pred->empty())
+ return true;
+
+ // Otherwise, check the last instruction.
+ const MachineInstr &LastInst = Pred->back();
+ return !LastInst.getDesc().isBarrier();
+}
+